Is pre-processing used in deep learning?
Yes, sure, data pre-processing is also done in deep learning. For example, we often normalize (or scale) the inputs to neural networks. If the inputs are images, we often resize them so that they all have the same dimensions. Of course, the pre-processing step that you apply depends on your data, neural network, and task.
Here or here are two examples of implementations that perform a pre-processing step (normalization in the second case). You can find more explanations and examples here and probably here too.